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1.
青藏高原和亚洲夏季风动力学研究的新进展   总被引:4,自引:1,他引:3  
亚洲夏季风环流受海陆和伊朗高原—青藏高原大地形的热力作用调控.亚洲季风所释放的巨大潜热又对大气环流形成反馈.这种相互反馈过程十分复杂,揭示其物理过程对理解气候变化格局的形成和变化以及提高天气预报及气候预测的准确率十分重要.夏季北半球副热带对流层上层环流的主要特征是存在庞大的南亚高压(SAH)以及强大的对流层上层温度暖中心(UTTM).本文介绍了温度—加热垂直梯度(T-QZ)理论的发展,并用以揭示SAH和UTTM的形成机制.指出沿副热带欧亚大陆东部的季风对流潜热加热及其中西部的表面感热加热和高层长波辐射冷却是导致SAH和UTTM在南亚上空发展的原因.文中还介绍了Gill模型用于上部对流层研究的局限性及解决的办法.  相似文献   
2.
Simulations of tropical intraseasonal oscillation(TISO) in SAMIL,the Spectral Atmospheric Model from the Institute of Atmospheric Physics(IAP) State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics(LASG) coupled and uncoupled general circulation models were comprehensively evaluated in this study.Compared to the uncoupled model,the atmosphere-ocean coupled model improved the TISO simulation in the following aspects:(1) the spectral intensity for the 30-80-day peak eastward periods was more realistic;(2) the eastward propagation signals over western Pacific were stronger;and(3) the variance distribution and stronger signals of Kelvin waves and mixed Rossby gravity waves were more realistic.Better performance in the coupled run was assumed to be associated with a better mean state and a more realistic relationship between precipitation and SST.In both the coupled and uncoupled runs,the unrealistic simulation of the eastward propagation over the equatorial Indian Ocean might have been associated with the biases of the precipitation mean state over the Indian Ocean,and the unrealistic split of maximum TISO precipitation variance over the Pacific might have corresponded to the exaggeration of the double Intertropical Convergence Zone(ITCZ) structure in precipitation mean state.However,whether a better mean state leads to better TISO activity remains questionable.Notably,the northward propagation over the Indian Ocean during summer was not improved in the mean lead-lag correlation analysis,but case studies have shown some strong cases to yield remarkably realistic northward propagation in coupled runs.  相似文献   
3.
Earth System Models (ESMs) are fundamental tools for understanding climate-carbon feedback. An ESM version of the Flexible Global Ocean-Atmosphere-Land System model (FGOALS) was recently developed within the IPCC AR5 Coupled Model Intercomparison Project Phase 5 (CMIP5) modeling framework, and we describe the development of this model through the coupling of a dynamic global vegetation and terrestrial carbon model with FGOALS-s2. The performance of the coupled model is evaluated as follows. The simulated global total terrestrial gross primary production (GPP) is 124.4 PgC yr-I and net pri- mary production (NPP) is 50.9 PgC yr-1. The entire terrestrial carbon pools contain about 2009.9 PgC, comprising 628.2 PgC and 1381.6 PgC in vegetation and soil pools, respectively. Spatially, in the tropics, the seasonal cycle of NPP and net ecosystem production (NEP) exhibits a dipole mode across the equator due to migration of the monsoon rainbelt, while the seasonal cycle is not so significant in Leaf Area Index (LAI). In the subtropics, especially in the East Asian monsoon region, the seasonal cycle is obvious due to changes in temperature and precipitation from boreal winter to summer. Vegetation productivity in the northern mid-high latitudes is too low, possibly due to low soil moisture there. On the interannual timescale, the terrestrial ecosystem shows a strong response to ENSO. The model- simulated Nifio3.4 index and total terrestrial NEP are both characterized by a broad spectral peak in the range of 2-7 years. Further analysis indicates their correlation coefficient reaches -0.7 when NEP lags the Nifio3.4 index for about 1-2 months.  相似文献   
4.
中国地球气候系统模式的发展及其模拟和预估   总被引:4,自引:0,他引:4  
地球气候系统模式是开展多学科、多圈层集成研究的重要平台,其发展是国际地学领域特别是全球变化领域竞争的前沿。中国的地球气候系统模式研发工作始于20世纪80年代,最近10年得到快速发展。研发格局上已经形成中国科学院、有关部委和高校三足鼎立的局面。文中在简要回顾中国地球气候系统模式早期发展历史的基础上,总结了中国参加第6次耦合模式比较计划的9个地球气候系统模式的技术特点,初步评估了中国4个模式对全球和东亚气候模拟的基本性能,分析了其在4种共享社会经济路径情景下对全球降水与温度的预估变化及其与平衡态气候敏感度的联系。最后,结合国际态势,从发展的角度提出未来中国气候模式研发工作需要加强的8个方向。   相似文献   
5.
Recent Progress in the Impact of the Tibetan Plateau on Climate in China   总被引:14,自引:0,他引:14  
Studies of the impacts of the Tibetan Plateau (TP) on climate in China in the last four years are reviewed. It is reported that temperature and precipitation over the TP have increased during recent decades. From satellite data analysis, it is demonstrated that most of the precipitation over the TP is from deep convection clouds. Moreover, the huge TP mechanical forcing and extraordinary elevated thermal forcing impose remarkable impacts upon local circulation and global climate. In winter and spring, stream flow is deflected by a large obstacle and appears as an asymmetric dipole, making East Asia much colder than mid Asia in winter and forming persistent rainfall in late winter and early spring over South China. In late spring, TP heating contributes to the establishment and intensification of the South Asian high and the abrupt seasonal transition of the surrounding circulations. In summer, TP heating in conjunction with the TP air pump cause the deviating stream field to resemble a cyclonic spiral, converging towards and rising over the TP. Therefore, the prominent Asian monsoon climate over East Asia and the dry climate over mid Asia in summer are forced by both TP local forcing and Eurasian continental forcing.
Due to the longer memory of snow and soil moisture, the TP thermal status both in summer and in late winter and spring can influence the variation of Eastern Asian summer rainfall. A combined index using both snow cover over the TP and the ENSO index in winter shows a better seasonal forecast.
On the other hand, strong sensible heating over the Tibetan Plateau in spring contributes significantly to anchor the earliest Asian monsoon being over the eastern Bay of Bengal (BOB) and the western Indochina peninsula. Qualitative prediction of the BOB monsoon onset was attempted by using the sign of meridional temperature gradient in March in the upper troposphere, or at 400 hPa over the TP. It is also demonstrated by a numerical experiment and theoretical study that the heating over the TP lea  相似文献   
6.
This study mainly introduces the development of the Flexible Global Ocean-Atmosphere-Land System Model: Grid-point Version 2 (FGOALS-g2) and the preliminary evaluations of its performances based on results from the pre-industrial control run and four members of historical runs according to the fifth phase of the Coupled Model Intercomparison Project (CMIP5) experiment design. The results suggest that many obvious improvements have been achieved by the FGOALS-g2 compared with the previous version,FGOALS-g1, including its climatological mean states, climate variability, and 20th century surface temperature evolution. For example,FGOALS-g2 better simulates the frequency of tropical land precipitation, East Asian Monsoon precipitation and its seasonal cycle, MJO and ENSO, which are closely related to the updated cumulus parameterization scheme, as well as the alleviation of uncertainties in some key parameters in shallow and deep convection schemes, cloud fraction, cloud macro/microphysical processes and the boundary layer scheme in its atmospheric model. The annual cycle of sea surface temperature along the equator in the Pacific is significantly improved in the new version. The sea ice salinity simulation is one of the unique characteristics of FGOALS-g2, although it is somehow inconsistent with empirical observations in the Antarctic.  相似文献   
7.
张丽霞  周天军  吴波  包庆 《气象学报》2008,66(6):968-981
文中评估了中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室(LASG/IAP)新一代耦合气候模式Fgoals_s1.1对热带降水年循环模态的模拟能力。通过与观测表层海温(SST)强迫的大气模式SAMIL试验结果比较,分析了海气耦合过程对年循环模态模拟效果的影响。结果表明Fgoals_s1.1能合理再现热带地区降水年循环模态的基本特征。Fgoals_s1.1模拟出了年平均降水场中的主要降水中心,但模拟的赤道和南太平洋降水偏多,而北太平洋降水则偏少。Fgoals_s1.1的季风模态降水呈现与观测一致的关于赤道反对称的特征,其模拟偏差大部分来自大气分量,尤其是在赤道外。Fgoals_s1.1的主要缺陷在于它对春秋非对称模态模拟能力低于单独大气模式,这主要是由于耦合模式模拟的SST距平的年循环位相与观测相反。SST纬向梯度的位相偏差使得太平洋沃克环流和印度洋的反沃克环流在春季强于秋季,最终导致模拟的春秋非对称模态的偏差。Fgoals_s1.1模拟的季风区范围接近观测,存在的问题在于模拟的西北太平洋季风区、东亚季风区都偏小。本文结果表明,大气模式偏差仅是Fgoals_s1.1在降水年循环模态模拟上的偏差的部分来源,改进模式模拟的SST,特别是赤道地区SST季节循环,是今后Fgoals_s1.1发展过程中急需解决的问题。  相似文献   
8.
The Flexible Global Ocean-Atmosphere-Land System model, Spectral Version 2 (FGOALS-s2) was used to simulate realistic climates and to study anthropogenic influences on climate change. Specifically, the FGOALS-s2 was integrated with Coupled Model Intercomparison Project Phase 5 (CMIP5) to conduct coordinated experiments that will provide valuable scientific information to climate research communities. The performances of FGOALS-s2 were assessed in simulating major climate phenomena, and documented both the strengths and weaknesses of the model. The results indicate that FGOALS-s2 successfully overcomes climate drift, and realistically models global and regional climate characteristics, including SST, precipitation, and atmospheric circulation. In particular, the model accurately captures annual and semi-annual SST cycles in the equatorial Pacific Ocean, and the main characteristic features of the Asian summer monsoon, which include a low-level southwestern jet and five monsoon rainfall centers. The simulated climate variability was further examined in terms of teleconnections, leading modes of global SST (namely, ENSO), Pacific Decadal Oscillations (PDO), and changes in 19th–20th century climate. The analysis demonstrates that FGOALS-s2 realistically simulates extra-tropical teleconnection patterns of large-scale climate, and irregular ENSO periods. The model gives fairly reasonable reconstructions of spatial patterns of PDO and global monsoon changes in the 20th century. However, because the indirect effects of aerosols are not included in the model, the simulated global temperature change during the period 1850–2005 is greater than the observed warming, by 0.6°C. Some other shortcomings of the model are also noted.  相似文献   
9.
The simulation characteristics of the seasonal evolution of subtropical anticyclones in the Northern Hemisphere are documented for the Flexible Global Ocean-Atmosphere-Land Systemmodel, Spectral Version 2 (FGOALS-s2), developed at the State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, the Institute of Atmospheric Physics. An understanding of the seasonal evolution of the subtropical anticyclones is also addressed. Compared with the global analysis established by the European Centre for Medium-Range Forecasts, the ERA-40 global reanalysis data, the general features of subtropical anticyclones and their evolution are simulated well in both winter and summer, while in spring a pronounced bias in the generation of the South Asia Anticyclone(SAA) exists. Its main deviation in geopotential height from the reanalysis is consistent with the bias of temperature in the troposphere. It is found that condensation heating (CO) plays a dominant role in the seasonal development of the SAA and the subtropical anticyclone over the western Pacific (SAWP) in the middle troposphere. The CO biases in the model account for the biases in the establishment of the SAA in spring and the weaker strength of the SAA and the SAWP from spring to summer. CO is persistently overestimated in the central-east tropical Pacific from winter to summer, while it is underestimated over the area from the South China Sea to the western Pacific from spring to summer. Such biases generate an illusive anticyclonic gyre in the upper troposphere above the middle Pacific and delay the generation of the SAA over South Asia in April. In midsummer, the simulated SAA is located farther north than in the ERA-40 data owing to excessively strong surface sensible heating (SE) to the north of the Tibetan Plateau. Whereas, the two surface subtropical anticyclones in the eastern oceans during spring to summer are controlled mainly by the surface SE over the two continents in the Northern Hemisphere, which are simulated reasonably well, albeit with their centers shifted westwards owing to the weaker longwave radiation cooling in the simulation associated with much weaker local stratiform cloud. Further improvements in the related parameterization of physical processes are therefore identified.  相似文献   
10.
青藏高原感热气泵影响亚洲夏季风的机制   总被引:5,自引:1,他引:5  
本文回顾了二十年来关于青藏高原感热驱动气泵(TP-SHAP)及其影响亚洲夏季风的研究进展,并从能量(θ)、位涡—加热(PV–Q)、和角动量守恒(AMC)的不同角度阐述其影响机制。指出高原斜坡上的表面感热加热改变了移向高原的大气质块的能量从而出现垂直抽吸的重要性。强调了高原加热产生的位涡强迫在近地层制造了强度大范围广的、环绕高原的气旋式环流,把丰沛的水汽从海洋输运到大陆,为季风对流降水提供充足的水汽条件。证明高原加热还通过改变其上空的温、压场的结构从而制造出高原上空近对流层顶的绝对涡度和位涡的最小值,在角动量平衡约束下,在亚洲季风区激发出与Hadley环流反向的季风经圈环流,从而为季风发生发展提供了大范围上升运动的背景。文中还对近年来有关青藏高原影响亚洲夏季风机制的讨论进行概述,并展望了未来的研究方向。  相似文献   
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